The present application relates to a detector array of an x-ray imaging system (e.g., a radiography and/or CT system). It finds particular application with x-ray imaging systems that comprise large detector arrays (e.g., that may span 1 meter or more in length and/or ½ meter in width), but also applies to smaller detector arrays as well. Such detector arrays are commonly used in medical, security, and/or industrial x-ray imaging systems, for example.
X-ray imaging systems, such as projection radiography systems, computed tomography (CT) systems, line scanners, etc., provide information, or images, of the inside of an object under examination (e.g., interior aspects of an object under examination). That is, an object under examination by the x-ray imaging system is exposed to radiation, and one or more images are formed based upon the radiation absorbed by the object, or rather an amount of radiation that is able to pass through the object. Typically, highly dense objects absorb (e.g., attenuate) more radiation than less dense objects, and thus an object having a higher density, such as a bone or metal object, for example, will appear differently than less dense objects, such as fatty tissue or clothing, for example.
Traditionally x-ray images were formed using x-ray film. The film was exposed to radiation, or light yielded from the radiation (e.g., if intensifying screens were placed between the film and the radiation source), and a visible pattern of metallic black silver was produced on the film. The degree of blackening (e.g., the amount of metallic black silver produced) depended upon the intensity of the radiation (e.g., the magnitude of radiation absorbed by the object). Thus, the detector array was essentially comprised of an x-ray film and possibly one or more intensifying screens.
More recently, the x-ray film and the intensifying screens have been replaced with digital detector arrays (e.g., such as those commonly found in digital radiography and CT systems) that are configured to convert radiation, either directly or indirectly, into electric current that is measured to yield electrical signals. The amount of electric current measured is proportional to the number of radiation photons that impacted the digital detector array and can be used to create an image(s) of the object under examination.
It will be appreciated to those skilled in the art that there are two basic types of digital detector arrays, direct conversion detector arrays and indirect conversion detector arrays. Direct conversion detector arrays are typically configured to convert detected radiation directly into electric charge using a crystalline or amorphous material, for example. Indirect conversion detector arrays are generally configured to convert detected radiation into another medium, typically light, before the electric charge is produced. Thus, for example, indirect conversion detector arrays may convert radiation into light using a scintillator material (e.g., Cadmium Tungstate, Bismuth Germanate, Cesium Iodide, Sodium Iodide, etc.) and may subsequently convert the light into electric charge using a photodetector array (e.g., a plurality of photodiodes). Generally, in both direct and indirect conversion detector arrays, the electric charge is detected/measured using an electronic, pixelated array (e.g., a thin-film transistor (TFT) array comprising a two-dimensional (2D) capacitor array).
While digital detector arrays have proven effective for imaging (e.g., and have many benefits over x-ray film), the cost of manufacturing a digital detector array can cost several tens of thousands of dollars or more, depending upon its size, among other things. For large scale x-ray imaging systems that may comprise detector arrays measuring one meter by one-half a meter, for example, such as those comprised in baggage systems and/or systems commonly found in industrial applications, the cost of a detector array may be approximately 30% of the total system cost. Such cost may make implementation of an x-ray imaging system cost prohibitive in some applications.